The association of human emphysema with deficiency of the serum protease inhibitor alpha-1-antitrypsin (AAT) has stimulted efforts to discover the cause of AAI deficiency as a first step to developing prophylaxis and therapy for the illness and disability it causes. Existing evidence implicates the liver as a site of AAI synthesis rather than simple storage but only one study, using embryonic and fetal liver, has shown synthesis of AAT that was identified by specific antibody. Efforts to understand the mechanism of AAT deficiency would be aided greatly by a system capable of human AAT synthesis and secretion in vitro which would permit manipulations and control of experimental conditions that are not possible in human subjects. The objectives of the proposed research are: (1) to identify the organ sites of AAT synthesis and secretion, (2) to isolate cultured cells that synthesize and secrete human AAT in vitro, and (3) to use these cells to study the action of genes producing AAT deficiency. To detect AAT synthesis, mouse and human autopsy liver and other tissues will be incubated with medium containing C14-leucine, and concentrated medium will be subjected to crossed antigen-antibody electrophoresis with carrier serum, followed by radioautography. To isolate cultured cells that synthesize and secrete human AAT, two approaches will be used: (A) Rodent hepatoma cells secreting AAT will be fused with human leukocytes to produce somatic cell hybrids which will be tested for human AAT synthesis and secretion in medium and cell contents with a specific radioimmunoassay. Activation of human albumin genes has been shown in hybrid cells of the same type. Hybrids made with leukocytes from patients with AAT deficiency will be tested for intracellular accumulation of AAT as a manifestation in vitro of the accumulation of AAT in liver cells that occurs in patients with partial and severe AAT deficiency. (B) Cells cultured from autopsy liver from people with normal, partial deficiency and severe deficiency of AAT will be tested for secretion and accumulation of AAT. The movement of labeled AAT will be studied by using an ultracentrifuge to fractionate into organelles cells synthesizing and secreting or accumulating human AAT.